Water-in-oil capsule manufacture process and microcapsules produced by such process

ABSTRACT

A novel method of forming water in oil microcapsules is disclosed. According to the invention microcapsules are obtained by steps comprising dispersing an oil soluble amine modified polyfunctional polyvinyl monomer and an oil soluble bi- or polyfunctional vinyl monomer along with a thermal or UV free radical initiator (optionally included in one or both of the oil or water phases) and an organic acid into an internal phase oil; heating or UV exposing for a time (and temperature) sufficient to oligomerize the amine modified polyfunctional polyvinyl monomer and oil soluble bi- or polyfunctional vinyl monomer forming a pre-polymer. Thereafter the process involves adding to the oil phase oil a water phase comprising a dispersion in water of an anionic emulsifier (and optionally initiator), and adding an emulsifying agent. Emulsifying the water phase into the oil phase (W/O) is controlled through the quantity of water employed. The emulsion is then UV exposed or heated for a time (and temperature) sufficient to decompose the free radical initiators in the oil and/or water phases; thereby forming microcapsule wall material at the interface of the water and oil phases.

BACKGROUND OF THE INVENTION

This application under 35 U.S.C. §111(a) claims priority to provisionalU.S. application Ser. No. 60/683,356 filed May 23, 2005 and incorporatedherein by reference.

1. Field of the Invention

This invention relates to capsule manufacturing processes andmicrocapsules produced by such processes.

2. Description of the Related Art

Various processes for microencapsulation, and exemplary methods andmaterials are set forth in Schwantes (U.S. Pat. No. 6,592,990), Nagaiet. al. (U.S. Pat. No. 4,708,924), Baker et. al. (U.S. Pat. No.4,166,152), Wojciak (U.S. Pat. No. 4,093,556), Matsukawa et. al. (U.S.Pat. No. 3,965,033), Matsukawa (U.S. Pat. No. 3,660,304), Ozono (U.S.Pat. No. 4,588,639), Irgarashi et. al. (U.S. Pat. No. 4,610,927), Brownet. al. (U.S. Pat. No. 4,552,811), Scher (U.S. Pat. No. 4,285,720),Shioi et. al. (U.S. Pat. No. 4,601,863), Kiritani et. al. (U.S. Pat. No.3,886,085), Jahns et. al. (U.S. Pat. Nos. 5,596,051 and 5,292,835),Matson (U.S. Pat. No. 3,516,941), Chao (U.S. Pat. No. 6,375,872), Foriset. al. (U.S. Pat. Nos. 4,001,140; 4,087,376; 4,089,802 and 4,100,103),Greene et. al. (U.S. Pat. Nos. 2,800,458; 2,800,457 and 2,730,456),Clark (U.S. Pat. No. 6,531,156), Saeki et. al. (U.S. Pat. Nos. 4,251,386and 4,356,109), Hoshi et. al. (U.S. Pat. No. 4,221,710), Hayford (U.S.Pat. No. 4,444,699), Hasler et. al. (U.S. Pat. No. 5,105,823), Stevens(U.S. Pat. No. 4,197,346), Riecke (U.S. Pat. No. 4,622,267), Greiner et.al. (U.S. Pat. No. 4,547,429), and Tice et. al. (U.S. Pat. No.5,407,609), among others and as taught by Herbig in the chapter entitled“Encapsulation” in Kirk Othmer, Encyclopedia of Chemical Technology,V.13, Second Edition, pages 436456 and by Huber et. al. in “CapsularAdhesives”, TAPPI, Vol. 49, No. 5, pages 41A-44A, May 1966, all of whichare incorporated herein by reference.

More particularly, U.S. Pat. Nos. 2,730,456, 2,800,457; and 2,800,458describe methods for capsule formation. Other useful methods formicrocapsule manufacture are: U.S. Pat. Nos. 4,001,140; 4,081,376 and4,089,802 describing a reaction between urea and formaldehyde; U.S. Pat.No. 4,100,103 describing reaction between melamine and formaldehyde;British Pat. No. 2,062,570 describing a process for producingmicrocapsules having walls produced by polymerization of melamine andformaldehyde in the presence of a styrenesulfonic acid. Microcapsulesare also taught in U.S. Pat. Nos. 2,730,457 and 4,197,346. Formingmicrocapsules from urea-formaldehyde resin and/or melamine formaldehyderesin is disclosed in U.S. Pat. Nos. 4,001,140; 4,081,376, 4,089,802;4,100,103; 4,105,823; and 4,444,699. Alkyl acrylate-acrylic acidcopolymer capsules are taught in U.S. Pat. No. 4,552,811. Each patentdescribed throughout this application is incorporated herein byreference to the extent each provides guidance regardingmicroencapsulation processes and materials.

Interfacial polymerization is a process wherein a microcapsule wall of apolyamide, an epoxy resin, a polyurethane, a polyurea or the like isformed at an interface between two phases. U.S. Pat. No. 4,622,267discloses an interfacial polymerization technique for preparation ofmicrocapsules. The core material is initially dissolved in a solvent andan aliphatic diisocyanate soluble in the solvent mixture is added.Subsequently, a nonsolvent for the aliphatic diisocyanate is added untilthe turbidity point is just barely reached. This organic phase is thenemulsified in an aqueous solution, and a reactive amine is added to theaqueous phase. The amine diffuses to the interface, where it reacts withthe diisocyanate to form polymeric polyurethane shells. A similartechnique, used to encapsulate salts which are sparingly soluble inwater in polyurethane shells, is disclosed in U.S. Pat. No. 4,547,429U.S. Pat. No. 3,516,941 teaches polymerization reactions in which thematerial to be encapsulated, or core material, is dissolved in anorganic, hydrophobic oil phase which is dispersed in an aqueous phase.The aqueous phase has dissolved materials forming aminoplast resin whichupon polymerization form the wall of the microcapsule. A dispersion offine oil droplets is prepared using high shear agitation. Addition of anacid catalyst initiates the polycondensation forming the aminoplastresin within the aqueous phase, resulting in the formation of anaminoplast polymer which is insoluble in both phases. As thepolymerization advances, the aminoplast polymer separates from theaqueous phase and deposits on the surface of the dispersed droplets ofthe oil phase to form a capsule wall at the interface of the two phases,thus encapsulating the core material. This process produces themicrocapsules. Polymerizations that involve amines and aldehydes areknown as aminoplast encapsulations. Urea-formaldehyde (UF),urea-resorcinol-formaldehyde (URF), urea-melamine-formaldehyde (UMF),and melamine-formaldehyde (MF), capsule formations proceed in a likemanner. In interfacial polymerization, the materials to form the capsulewall are in separate phases, one in an aqueous phase and the other in afill phase. Polymerization occurs at the phase boundary. Thus, apolymeric capsule shell wall forms at the interface of the two phasesthereby encapsulating the core material. Wall formation of polyester,polyamide, and polyurea capsules typically proceeds via interfacialpolymerization.

U.S. Pat. No. 5,292,835 teaches polymerizing esters of acrylic acid ormethacrylic acid with polyfunctional monomers. Specifically illustratedare reactions of polyvinylpyrrolidone with acrylates such as butanedioldiacrylate or methylmethacrylate together with a free radical initiator.

Common microencapsulation processes can be viewed as a series of steps.First, the core material which is to be encapsulated is typicallyemulsified or dispersed in a suitable dispersion medium. This medium istypically aqueous but involves the formation of a polymer rich phase.Most frequently, this medium is a solution of the intended capsule wallmaterial. The solvent characteristics of the medium are changed such asto cause phase separation of the wall material. The wall material isthereby contained in a liquid phase which is also dispersed in the samemedium as the intended capsule core material. The liquid wall materialphase deposits itself as a continuous coating about the disperseddroplets of the internal phase or capsule core material. The wallmaterial is then solidified. This process is commonly known ascoacervation.

Capsules made according to the invention can be made to better controlpermeability characteristics. Capsules made according to the inventionare surprisingly better able to contain liquid contents without leakageover time. The capsules can be made less leaky than those made bycomparable prior art processes. Alternatively permeability in certainapplications is desired. Through selection of wall material and controlof length of time of cross-linking or temperature of cross-linking,capsules can be made with differing permeability profiles from extremelytight with little to no leakage to capsules that have measurablepermeability useful where a measurable release rate over time isdesired.

The capsules according to the invention are useful with a wide varietyof capsule contents (“core materials”) including, by way of illustrationand without limitation, dyes, perfumes, fragrances, cleaning oils,polishing oils, flavorants, sweeteners, chromogens, pharmaceuticals,fertilizers, herbicides, scents, and the like. The microcapsule corematerials can include materials which alter rheology or flowcharacteristics, or extend shelf life or product stability. Essentialoils as core materials can include, for example, by way of illustrationwintergreen oil, cinnamon oil, clove oil, lemon oil, lime oil, orangeoil, peppermint oil and the like. Dyes can include fluorans, lactones,indolyl red, I6B, leuco dyes, all by way of illustration and notlimitation. The core material should be dispersible or sufficientlysoluble in the capsule internal phase material namely in the internalphase oil or soluble or dispersible in the monomers or oligomerssolubilized or dispersed in the internal phase oil. When the internalphase is water, the core material should be dispersible or sufficientlysoluble in the water phase. The invention is particularly useful toencapsulate volatile fragrances and flavorants. When a water phase isbeing microencapsulated, with the oil phase serving as the continuousphase, the core material should be soluble or dispersible in the waterphase so as to form a dispersion in water that can be emulsified intothe oil phase.

Low capsule permeability is a sought after characteristic ofmicrocapsules for many applications. Although various microencapsulationprocesses are known, a need has existed in particular for lowerpermeability and more durable capsules. Additionally, for certainapplications, low permeability capsules that are heat sensitive are alsodesirable.

In alternative embodiments, capsules according to the invention are alsoable to be fashioned with thermoplastic polymeric materials resulting inlow leakage heat sensitive capsules that could be opened with heat inaddition to conventional techniques such as pressure, scraping,friction, shearing, impact, or other energy input. The capsulesaccording to the invention can also be useful in applications withthermal print heads, or lasers, or other heating or impact elements. Inalternative embodiments, if a light stimulated material is included,light sensitive capsules are also feasible.

The permeability characteristics of the capsules disclosed herein haveversatility for a variety of applications. Wherever an internal phase isdesired to be held securely over time but available to be exuded orreleased upon fracture or breakage of the capsules such as withapplication of pressure, a low permeability capsule according to theinvention can be fashioned. Where measurable release is desired, morepermeable capsules can also be fashioned.

SUMMARY OF THE INVENTION

A novel method of forming water in oil, and oil in water microcapsulesis disclosed. According to the invention microcapsules are obtainedthrough either oil in water (O/W) or water in oil (W/O) emulsifications.In one embodiment microcapsules are obtained by steps comprisingdispersing an oil soluble amine modified polyfunctional polyvinylmonomer (or oligomer) and an oil soluble bi- or polyfunctional vinylmonomer or oligomer along with a free radical initiator such as an azoor peroxy initiator and an organic acid into an internal phase oil whichis a non-solvent for the water phase. The phase in excess is water withO/w emulsification. With W/O emulsifications the phase in excess orcontinuous phase is oil. The term internal phase oil is used forconvenience and simplicity to refer to the oil phase and to refer to thetype of oils conventionally used as the internal phase or contents ofmicrocapsules in conventional microencapsulation (with the W/Oemulsifications taught herein, the oil however ends up being thecontinuous phase. The water phase forms the capsule internal contents.The term “oil phase” is intended to refer to the oil phase oil.) The oilphase dispersion is heated for a time and temperature sufficient tooligomerize the amine modified polyfunctional polyvinyl monomer oroligomer and oil soluble bi- or polyfunctional vinyl monomer or oligomerforming a pre-polymer. The next step is adding to the oil phase a waterphase comprising a dispersion in water of an anionic emulsifier and anoptional second initiator which can be the same or different such as anazo or peroxy initiator. This water phase is emulsified into the oilphase (W/O) followed by heating for a time and temperature sufficient todecompose at least one of the free radical initiators, which can beplaced in either or both of the oil and/or water phases; thereby formingmicrocapsule wall material at the interface of the water and oil phases.A third heating step is used to polymerize the formed wall material andin the process, preferably decomposing any remaining initiator.

In a second embodiment, microcapsules are obtained by steps comprisingdispersing an oil soluble amine modified ethoxylated trimethylol propanetriacrylate and an oil soluble diethylene glycol dimethacrylate alongwith a free radical initiator such as an azo initiator and an organicacid into an internal oil phase; heating for time and temperaturesufficient to oligomerize the amine modified ethoxylated trimethylolpropane triacrylate and a diethylene glycol dimethacrylate forming apre-polymer; then, adding to the oil phase a water phase comprising adispersion of water, and an anionic emulsifier acid, and an optionalsecond initiator. The water phase is then emulsified into the oil phase(W/O) and heated for a time and temperature sufficient to decompose atleast one of the free radical initiators in either or both of the oiland water phases; thereby forming microcapsule wall material at theinterface of the water and oil phases.

In an alternative embodiment involving an oil in water (O/W) emulsion,microcapsules are obtained by steps comprising dispersing an oil solubleamine modified polyfunctional polyvinyl monomer and an oil soluble bi-or polyfunctional vinyl monomer or oligomer along with a free radicalazo initiator and an organic acid into an internal phase; then, heatingfor a time and temperature sufficient to oligomerize or furtheroligomerize the amine modified polyfunctional polyvinyl monomer oroligomer and oil soluble bi- or polyfunctional vinyl monomer forming apre-polymer; then, adding to the oil phase a water phase in excesscomprising a dispersion in water of an anionic emulsifier and anoptional second initiator, and adding an emulsifying agent; emulsifyingthe oil phase into the water phase; then heating for a time andtemperature sufficient to decompose the free radical initiators ineither or both of the oil and water phases; thereby forming microcapsulewall material at the interface of the water and oil phases.

In yet another embodiment involving an oil in water emulsion (O/W)process, microcapsules are obtained by steps comprising dispersing anoil soluble amine modified ethoxylated trimethylol propane triacrylateand an oil soluble diethylene glycol dimethacrylate along with a freeradical initiator such as an initiator and an organic acid into aninternal phase oil; heating for time and temperature sufficient tooligomerize the amine modified ethoxylated trimethylol propanetriacrylate and a diethylene glycol dimethacrylate forming apre-polymer; then, adding to the internal phase oil a water phasecomprising a dispersion of water, and an emulsifier such as apolyacrylic or polymethacrylic acid, emulsifying the oil phase into thewater phase; then heating for a time and temperature sufficient todecompose the free radical initiators in the oil and water phases;thereby forming microcapsule wall material at the interface of the waterand oil phases. Optionally, the free radical initiator can be includedin one or both of the oil and water phase.

In one embodiment the invention comprises microcapsules obtained bysteps comprising dispersing an oil soluble amine modified polyfunctionalpolyvinyl monomer or oligomer and an oil soluble bi- or polyfunctionalvinyl monomer or oligomer along with a free radical initiator and anorganic acid into an internal phase oil. A first heating step is usedcomprising, heating for a time and temperature sufficient to oligomerizeor further oligomerize the amine modified polyfunctional polyvinylmonomer or oligomer and oil soluble bi- or polyfunctional vinyl monomeroligomer forming a pre-polymer. A water phase comprising a dispersion inwater of an anionic emulsifier and a free radical initiator is added tothe internal phase oil. The water phase is emulsified into the oilphase. A second heating step is used comprising, heating for a time andtemperature sufficient to decompose the free radical initiators in theoil and water phases thereby forming microcapsule wall material at theinterface of and oil phases. Then a third heating step comprisingheating to a temperature equal to or greater than the second heatingstep temperature is used for a time sufficient to polymerize the wallmaterial. The free radical initiator is preferably selected from an azoor peroxy initiator. Oligomerization in one embodiment is accomplishedby heating, in the first heating step, to at least 55° C. for at leastone hour to form the prepolymer.

In an alternative embodiment the initiator in the oil phase decomposesat a first temperature and the initiator in the water phase decomposesat a second temperature. In a yet further embodiment the inventioncomprises microcapsules obtained by steps comprising dispersing an oilsoluble amine modified polyfunctional polyvinyl monomer or oligomer andan oil soluble bi- or polyfunctional vinyl monomer or oligomer alongwith a free radical initiator and an organic acid into an internal phaseoil; a first heating step comprising, heating for a time and temperaturesufficient to oligomerize or further oligomerize the amine modifiedpolyfunctional polyvinyl monomer or oligomer and oil soluble bi- orpolyfunctional vinyl monomer or oligomer forming a pre-polymer; addingto the internal phase oil a water phase in excess comprising adispersion in water of a polyacrylic or polymethacrylic acid and a freeradical initiator, and adding an emulsifying agent; emulsifying the oilphase into the water phase; and a second heating step comprising,heating for a time and temperature sufficient to decompose the freeradical initiator in the oil and water phases; thereby formingmicrocapsule wall material at the interface of the water and oil phases;and, a third heating step comprising heating to a temperature equal toor greater than the second heating step temperature for a timesufficient to polymerize the wall material.

In one embodiment the oligomerization is accomplished by heating, in thefirst heating step, is to at least 55° C. for at least one hour to formthe prepolymer and the third heating step is to at least 90° C. for atleast three hours. The second heating step comprised heating to atemperature equal to or greater than the first step, preferably greater.The second step temperature could involve dropping the temperatureslightly less than the first step, if only prolonged heating is neededto degrade any remaining free radical initiator.

In a yet further embodiment microcapsules are obtained by stepscomprising dispersing an oil soluble amine modified ethoxylatedtrimethylol propane triacrylate and an oil soluble diethylene glycoldimethacrylate along with free radical initiator and an organic acidinto an internal phase oil. A first heating step is used comprising,heating for time and temperature sufficient to oligomerize the aminemodified ethoxylated trimethylol propane triacrylate and a diethyleneglycol dimethacrylate forming a pre-polymer; then adding to the internalphase oil a water phase comprising a dispersion of water, and apolyacrylic or polymethacrylic acid, and adding an emulsifying agent;and emulsifying the water phase into the oil phase. A second heatingstep then comprises, heating for a time and temperature sufficient todecompose at least a portion of the free radical initiator in the oilphase, thereby forming microcapsule wall material at the interface ofthe water and oil phases; and a third heating step comprising heating toat least 90° C. for at least three hours to polymerize the wallmaterial.

In one embodiment the third heating step comprises heating to at least90° C. for at least three hours.

In a further embodiment a second initiator is added in addition to thewater phase and the initiator in the oil phase decomposes at a firsttemperature and the initiator in the water phase decomposes at a secondtemperature.

In a yet further embodiment, the initiators in the oil phase and thewater phase can be the same or different.

In a further embodiment microcapsules are obtained by steps comprising:dispersing an oil soluble amine modified polyfunctional polyvinylmonomer or oligomer and an oil soluble bi- or polyfunctional vinylmonomer or oligomer along with a free radical initiator and an organicacid into an internal phase oil; a first heating step comprising heatingfor a time and temperature sufficient to decompose at least some portionof the free radical initiator and thereby oligomerize or furtheroligomerize the amine modified polyfunctional polyvinyl monomer oroligomer and oil soluble bi- or polyfunctional vinyl monomer or oligomerforming a pre-polymer. Added to the internal phase oil is a water phasecomprising a dispersion in water of an anionic emulsifier, andemulsifying the water phase into the oil phase forming droplets of thewater phase dispersed in the oil phase. A second heating step comprisingheating for a time and temperature sufficient to decompose the remainingportion of free radical initiator thereby forming microcapsule wallmaterial from prepolymer at the interface of the water and oil phases. Athird heating step comprises heating to a temperature equal to orgreater than the second heating step temperature for a time sufficientto polymerize the wall material.

In one embodiment the oligomerization is accomplished by heating, in thefirst heating step, to at least 55° C. for at least one hour to form theprepolymer.

In a further embodiment the third heating step comprises heating to atleast 90° C. for at least three hours. In a further embodiment, theinitiator is added in addition to the water phase dispersion of anionicemulsifier, and the initiator in the oil phase decomposes at a firsttemperature and the initiator in the water phase decomposes at a secondtemperature. The initiators in the oil and water phases can be the sameor different.

In a further embodiment microcapsules are obtained by steps comprisingproviding an internal phase oil and a water phase containing a freeradical initiator in at least one of said phases, and dispersing an oilsoluble amine modified polyfunctional polyvinyl monomer or oligomer andan oil soluble bi- or polyfunctional vinyl monomer or oligomer and anorganic acid into the internal phase oil; then adding to the internalphase oil the water phase which further comprises a dispersion in waterof an anionic emulsifier, and emulsifying the water phase into the oilphase forming droplets of the water phase in the oil phase.

A first heating step comprises, heating for a time and temperaturesufficient to decompose the free radical initiator in at least the oilor water phase, and sufficient to oligomerize or further oligomerize theamine modified polyfunctional polyvinyl monomer or oligomer and oilsoluble bi- or polyfunctional vinyl monomer or oligomer forming apre-polymer and thereby forming microcapsule wall material at theinterface of the water and oil phases.

A second heating step comprises heating to a temperature equal to orgreater than the first heating step temperature for a time sufficient topolymerize the wall material.

In one embodiment the second heating step comprises heating to at least90° C. for at least three hours. Alternatively, initiator can be addedto both the oil and water phases. Optionally, the initiator in the oilphase can decompose at a first temperature and the initiator in thewater phase can decompose at a second temperature. The initiators in theoil and water phases can be the same or different.

In a yet further embodiment microcapsules are obtained by stepscomprising dispersing an oil soluble amine modified polyfunctionalpolyvinyl monomer or oligomer and an oil soluble bi- or polyfunctionalvinyl monomer or oligomer along with a free radical initiator and anorganic acid into an internal phase oil. A first heating step comprisesheating for a time and temperature sufficient to decompose at least someportion of the free radical initiator and thereby oligomerize the aminemodified polyfunctional polyvinyl monomer or oligomer and oil solublebi- or polyfunctional vinyl monomer or oligomer forming a pre-polymer.

Added to the internal phase oil is a water phase in excess, the waterphase comprising a dispersion in water of an anionic emulsifier.Emulsifying the oil phase into the water phase forms droplets of the oilphase dispersed in the water phase. High shear agitation is used. Asecond heating step comprises heating for a time and temperaturesufficient to decompose the remaining portion of free radical initiatorthereby forming microcapsule wall material from prepolymer at theinterface of the water and oil phases. The organic acid is believed tocontribute to the tendency of the prepolymer to gravitate to theinterface. This could be due to charge effects. A third heating stepcomprises heating to a temperature equal to or greater than the secondheating step temperature for a time sufficient to polymerize the wallmaterial.

In a yet further embodiment microcapsules are obtained by stepscomprising providing an internal phase oil and a water phase containinga free radical initiator in at least one of said phases; and dispersingan oil soluble amine modified polyfunctional polyvinyl monomer oroligomer and an oil soluble bi- or polyfunctional vinyl monomer oroligomer and an organic acid into the internal phase oil. Added to theinternal phase oil is a water phase in excess, the water phase furthercomprising a dispersion in water of an anionic emulsifier. The oil phaseis emulsified into the water phase forming droplets of the oil phase inthe oil phase. A first heating step comprises, heating for a time andtemperature sufficient to decompose the free radical initiator in atleast the oil or water phase, and sufficient to oligomerize or furtheroligomerize the amine modified polyfunctional polyvinyl monomer and oilsoluble bi- or polyfunctional vinyl monomer or oligomer forming apre-polymer and thereby forming microcapsule wall material at theinterface of the water and oil phases. A second heating step comprisingheating to a temperature equal to or greater than the first heating steptemperature for a time sufficient to polymerize the wall material.

In a yet further embodiment microcapsules are obtained by stepscomprising providing an internal phase oil and a water phase containinga free radical UV initiator and free radical thermal initiator in atleast one of said phases; dispersing an oil soluble amine modifiedpolyfunctional polyvinyl monomer or oligomer and an oil soluble bi- orpolyfunctional vinyl monomer or oligomer and an organic acid into theinternal phase oil; and adding to the internal phase oil the water phasewhich further comprises a dispersion in water of an anionic emulsifier,and emulsifying with high shear agitation the water phase into the oilphase forming droplets of the water phase in the oil phase. A first freeradical initiating step comprises, exposing with UV light the waterphase and oil phase emulsion for a time sufficient to decompose the UVfree radical initiator in at least the oil or water phase, andsufficient to oligomerize or further oligomerize the amine modifiedpolyfunctional polyvinyl monomer or oligomer and oil soluble bi- orpolyfunctional vinyl monomer or oligomer forming a pre-polymer andthereby forming microcapsule wall material at the interface of the waterand oil phases. A second free radical initiating step comprising heatingto a temperature sufficient to decompose the free radical thermalinitiator and heating for a time sufficient to polymerize the wallmaterial.

In a further embodiment the free radical initiators can each be selectedfrom an azo initiator. In one embodiment the heating step involvesheating to at least 55° C. for at least one hour to polymerize the wallmaterial. The heating step can comprise heating to at least 90° C. forat least three hours. Other temperatures and times can be used in theother embodiments. Optionally, initiator is added to both the oil andwater phases. In one embodiment the initiator in the oil phasedecomposes upon exposure to UV light and the initiator in the waterphase decomposes at a first selected temperature. The initiators in theoil and water phases can be the same or different. In one embodiment theinitiators are both UV initiators and the second free radical initiatingstep comprises exposing to UV light for a time sufficient to polymerizethe wall material.

In a yet further embodiment microcapsules are obtained by stepscomprising dispersing an oil soluble amine modified polyfunctionalpolyvinyl monomer or oligomer and an oil soluble bi- or polyfunctionalvinyl monomer or oligomer along with a UV free radical initiator and anorganic acid into an internal phase oil. A first free radical initiatingstep comprising exposing with UV light for a time sufficient todecompose at least some portion of the free radical initiator andthereby oligomerize the amine modified polyfunctional polyvinyl monomeror oligomer and oil soluble bi- or polyfunctional vinyl monomer oroligomer forming a pre-polymer. A water phase in excess, is added to theinternal phase oil. The water phase comprises a dispersion in water ofan anionic emulsifier. Emulsifying the oil phase into the water phaseusing high shear agitation form droplets of the oil phase dispersed inthe water phase. A second free radical initiating step comprisesexposing with UV light for a time sufficient to decompose the remainingportion of free radical initiator thereby forming microcapsule wallmaterial from prepolymer at the interface of the water and oil phases. Athird free radical initiating step comprises generating free radicalsfor a time sufficient to polymerize the wall material. In one embodimentthe free radical initiator is selected from a phenyl ketone,benzoinether, benzoil ketal, or azo initiator. In an alternateembodiment the oligomerization is accomplished by exposing to UV, lightin the first free radical initiating step, for at least one hour to formthe prepolymer.

In a further embodiment the third free radical initiating step comprisesexposing to UV for at least three hours. A second initiator can be addedin addition to the oil phase and the initiator in the oil phase can beselected to decompose at a set first temperature (based on half life ofinitiator, as is commonly understood with free radical initiators).

In a yet further embodiment microcapsules are obtained by stepscomprising providing an internal phase oil and a water phase containinga first free radical UV initiator in at least one of said phases, anddispersing an oil soluble amine modified polyfunctional polyvinylmonomer or oligomer and an oil soluble bi- or polyfunctional vinylmonomer or oligomer and an organic acid into the internal phase oil.Added to the internal phase oil is the water phase in excess. The waterphase further comprises a dispersion in water of an anionic emulsifier.Emulsifying the oil phase into the water phase forms droplets of the oilphase in the water phase.

A first free radical initiating step comprises exposing with UV lightfor a time sufficient to decompose the free radical initiator in atleast the oil or water phase, and sufficient to oligomerize or furtheroligomerize the amine modified polyfunctional polyvinyl monomer and oilsoluble bi- or polyfunctional vinyl monomer or oligomer forming apre-polymer thereby forming microcapsule wall material at the interfaceof the water and oil phases. A second free radical initiating stepcomprises exposing with UV light for a time sufficient to polymerize thewall material or heating for a time and temperature sufficient topolymerize the wall material. Optionally the free radical initiator isselected from an azo initiator. The first free radical initiating stepcan involve exposure with a UV light source or an electron beam for atleast one hour.

The second heating step optionally can comprise heating to at least 90°C. for at least three hours in certain embodiments. A second initiatorcan be added in addition to the water and oil phase and wherein thesecond initiator can be selected to decompose at a first temperature.Optionally, the first initiator is added to both the oil phase and thewater phase with the first initiators being the same or different ineach phase. The first initiators can be UV initiators, and the secondinitiator can be a thermal free radical initiator. Other such variationswill be readily evident to the skilled artisan.

DETAILED DESCRIPTION

The present invention teaches novel processes for microencapsulationinvolving water in oil, or oil in water emulsifications, andmicrocapsules obtained by such processes.

More particularly, the present invention in one embodiment is a processof obtaining microcapsules by dispersing an oil soluble amine modifiedpolyfunctional polyvinyl monomer or oligomer and an oil soluble bi- orpolyfunctional vinyl monomer or oligomer along with a free radicalinitiator, such as an azo or peroxy initiator, and an organic acid intoan internal phase oil. This dispersion is heated for a time andtemperature sufficient to oligomerize or further oligomerize the aminemodified polyfunctional polyvinyl monomer and oil soluble bi- orpolyfunctional vinyl monomer or oligomer to form a prepolymer. To thisinternal phase oil and prepolymer, a water phase is added comprising adispersion in water of an anionic emulsifier or an initiator. The waterphase in one embodiment is emulsified into the oil phase (W/O). Thedispersion is then heated for a time and temperature sufficient todecompose the free radical initiator, which can be placed in one or bothof the oil and water phases. Microcapsule wall material is therebyformed at the interface of the water and oil phases. A third heatingstep is used to polymerize or harden the formed wall material andusefully to decompose remaining initiator. Decompose the free radicalinitiator means that the initiator is consumed and in the processgenerates free radicals for furthering propagation of polymerizationreaction of the monomers and oligomers.

In forming the capsules of the invention, the emulsion is usually milledto a size of 0.1 to 80 microns, preferably 0.5 to 10 microns, morepreferably 1 to 8 microns. Larger sizes for particular applications arealso feasible.

Unlike conventional microencapsulation processes, the W/O and O/wprocesses taught herein employing an organic acid are believed to drivewall material from the oil phase to the oil water interface, though theapplication and invention should not be construed as limited to thisproposed mechanism.

The invention teaches novel processes for microencapsulation using waterin oil, or alternatively oil in water emulsifications. The capsules bythe process of the invention enable a low permeability or controlledpermeability capsule to be fashioned. Permeability can be controlledthrough wall material selection, through control of degree ofcross-linking, by controlling temperature of cross-linking, bycontrolling length of time of cross-linking or with UV initiated systemsby controlling intensity of UV light and duration.

In an alternative embodiment, the present invention is a process ofobtaining microcapsules by dispersing an oil soluble amine modifiedpolyfunctional polyvinyl monomer or oligomer and an oil soluble bi- orpolyfunctional vinyl monomer or oligomer along with a free radicalinitiator, such as a peroxy or azo initiator, and an organic acid intoan internal phase oil. This dispersion is heated for a time andtemperature sufficient to oligomerize or further oligomerize the aminemodified polyfunctional polyvinyl monomer and oil soluble bi- orpolyfunctional vinyl monomer to form a prepolymer. To this internalphase oil and prepolymer, a water phase is added in excess comprising adispersion in water of an anionic emulsifier and optionally, a freeradical initiator. The oil phase in this embodiment is emulsified intothe water phase (O/W). The dispersion is then heated for a time andtemperature sufficient to decompose the free radicals, positioned in oneor both of the oil and water phases. Microcapsule wall material isthereby formed at the interface of the water and oil phases.

In yet another embodiment, the invention is a process of obtainingmicrocapsules by dispersing an oil soluble amine modified ethoxylatedpropane triacrylate and an oil soluble diethylene glycol dimethacrylatealong with a free radical initiator and an organic acid into an internalphase oil. This dispersion is heated for a time and temperaturesufficient to oligomerize the amine modified ethoxylated trimethylolpropane triacrylate and a diethylene glycol dimethacrylate forming aprepolymer. To this internal phase oil and prepolymer, a water phase isadded comprising a dispersion in water of an anionic emulsifiers such asa polyacrylic or polymethyacrylic acid and an initiator such as an azoor peroxy initiator. The water phase is emulsified into the (W/O) oilphase (or alternatively the oil phase is emulsified into the water phase(O/W), if an excess of water is used). The dispersion is then heated fora time and temperature sufficient to decompose the free radicalinitiator which can be in one or both of the oil and water phases.Microcapsule wall material is thereby formed at the interface of thewater and oil phases.

Preferred amine modified polyfunctional polyvinyl monomers include aminemodified ethoxylated trimethylol propane triacrylate, ethoxylatedaliphatic, acrylated amines, such as diacrylate amines, triacrylateamines dimethacrylate amines, amine modified polyetheracrylates andamine modified polyethermethacrylates.

Preferred bi- or polyfunctional vinyl monomers include by way ofillustration and not limitation, allyl methacrylate; triethylene glycoldimethacrylate; ethylene glycol dimethacrylate, diethylene glycoldimethacrylate, aliphatic or aromatic urethane diacrylates, difunctionalurethane acrylates, ethoxylated aliphatic difunctional urethanemethacrylates, aliphatic or aromatic urethane dimethacrylates, epoxyacrylates, epoxymethacrylates; tetraethylene glycol dimethacrylate;polyethylene glycol dimethacrylate; 1,3 butylene glycol diacrylate;1,4-butanediol dimethacrylate; 1,4-butaneidiol diacrylate; diethyleneglycol diacrylate; 1,6 hexanediol diacrylate; 1,6 hexanedioldimethacrylate; neopentyl glycol diacrylate; polyethylene glycoldiacrylate; tetraethylene glycol diacrylate; triethylene glycoldiacrylate; 1,3 butylene glycol dimethacrylate; tripropylene glycoldiacrylate; ethoxylated bisphenol diacrylate; ethoxylated bisphenoldimethylacrylate; dipropylene glycol diacrylate; alkoxylated hexanedioldiacrylate; alkoxylated cyclohexane dimethanol diacrylate; propoxylatedneopentyl glycol diacrylate, trimethylolpropane trimethacrylate;trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylatedtrimethylolpropane triacrylate, propoxylated trimethylolpropanetriacrylate, propoxylated glyceryl triacrylate, ditrimethylolpropanetetraacrylate, dipentaerythritol pentaacrylate, ethoxylatedpentaerythritol tetraacrylate.

The organic acid can be selected from various acids such as carboxyacids, with monoalkyl maleates such as monomethyl, monoethyl ormonobutyl maleate being preferred, with monobutyl maleate being mostpreferred. Other organic acids that can be usefully employed in theinvention include, organic sulfonic acids such as alkyl benezenesulfonic acid, more particularly linear alkyl benzene sulfonic acid,tridecylbenzene sulfonic acid, more particularly linear trialkyl benzenesulfonic acid such as linear tridecyl benzene sulfonic acid,alkyldiphenyloxide sulfonic acid, preferably dodecyl diphenyloxidedisulfonic acid, more particularly branched C12 diphenyl oxidedisulfonic acid, alkylbenzene sulfonic acid, more particularly, dodecylbenzene sulfonic acid, dialkyl naphthalene disulfonic acid, moreparticularly dinonylnaphthalene disulfonic acid, 4-hydrozino benzenesulfonic acid and the like. Desirably the organic acid is selected to bedispersible in the oil phase and sparingly soluble in, the water phase.

Anionic emulsifiers include by way of illustrating and not limitation,water-soluble salts of alkyl sulfates, alkyl ether sulfates, alkylisothionates, alkyl carboxylates, alkyl sulfosuccinates, alkylsuccinamates, alkyl sulfate salts such as sodium dodecyl sulfate, alkylsarcosinates, alkyl derivatives of protein hydrolyzates, acylaspartates, alkyl or alkyl ether or alkylaryl ether phosphate esters,sodium dodecyl sulphate, phospholipids or lecithin, or soaps, sodium,potassium or ammonium stearate, oleate or palmitate, alkylarylsulfonicacid salts such as sodium dodecylbenzenesulfonate, sodiumdialkylsulfosuccinates, dioctyl sulfosuccinate, sodiumdilaurylsulfosuccinate, poly(styrene sulfonate) sodium salt,isobutylene-maleic anhydride copolymer, gum arabic, sodium alginate,carboxymethylcellulose, cellulose sulfate and pectin, poly(styrenesulfonate), isobutylene-maleic anhydride copolymer, gum arabic,carrageenan, sodium alginate, pectic acid, tragacanth gum, almond gumand agar; semi-synthetic polymers such as carboxymethyl cellulose,sulfated cellulose, sulfated methylcellulose, carboxymethyl starch,phosphated starch, lignin sulfonic acid; and synthetic polymers such asmaleic anhydride copolymers (including hydrolyzates thereof),polyacrylic acid, polymethacrylic acid, acrylic acid butyl acrylatecopolymer or crotonic acid homopolymers and copolymers,vinylbenzenesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acidhomopolymers and copolymers, and partial amide or partial ester of suchpolymers and copolymers, carboxymodified polyvinyl alcohol, sulfonicacid-modified polyvinyl alcohol and phosphoric acid-modified polyvinylalcohol, phosphated or sulfated tristyrylphenol ethoxylates. The amountof anionic emulsifier is anywhere from about 0.1 to about 40 percent byweight of all constitutents, more preferably from 0.5 to about 10percent, more preferably 0.5 to 5 percent by weight. Typicallyemulsifier is employed at 2 to about 10% by weight.

After solvent, the amine modified polyfunctional polyvinyl monomer andthe oil soluble bi- or poly functional vinyl monomers are the largerconstituents by weight used in a relative ratio of from about 0.5:1 toabout 1:3 preferably from about 1:1 to about 1:2.

The average molecular weight of the monomers initially is in thehundreds of daltons. For the oligomer molecular weights are in thethousands to tens of thousands of daltons. Prepolymers accordingly arehigher molecular weight still. Prepolymers are an intermediate block ofoligomers and monomers eventually forming a polymer. The monomer oroligomers should be selected to be soluble or dispersible in the oilphase.

For example, assuming a system of about 600 grams with solvent, thelargest constitutents are typically solvent, 10 to 70 weight percent,preferably 35-65 weight percent oil phase solvent and oil; 10 to 70percent, preferably 35-65weight percent water; 0.1 to 20 weight percent,usually 0.5 to 8 weight percent, preferably 2 to 6 weight percent, bi-or polyfunctional vinyl monomer or oligomer; 0.1 to 20 weight percent,usually 0.5 to 8 weight percent, preferably 2 to about 4 weight percent,amine modified amine modified polyfunctional monomer or oligomer.Initiator is 10% or less, usually about 1% or less, preferably 0.5% byweight or less and more preferably 0.1% or less.

As will be evident, the amount of the respective solvent or oil can beincreased or decreased as needed for rheology and depending on whetheran W/O or O/W system is desired.

Preferred free radical initiators include peroxy initiators, azoinitiators, peroxides, and compounds such as2,2′-azobismethylbutyronitrile, dibenzoyl peroxide. More particularly,and without limitation the free radical initiator can be selected fromthe group of initiators comprising an azo or peroxy initiator, such asperoxide, dialkyl peroxide, alkyl peroxide, peroxyester,peroxycarbonate, peroxyketone and peroxydicarbonate, 2,2′-azobis(isobutylnitrile), 2,2′-azobis(2,4-dimethylpentanenitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(2-methylpropanenitrile),2,2′-azobis (methylbutyronitrile), 1,1′-azobis(cyclohexanecarbonitrile), 1,1′-azobis(cyanocyclohexane), benzoylperoxide, decanoyl peroxide; lauroyl peroxide; benzoyl peroxide,di(n-propyl) peroxydicarbonate, di(sec-butyl) peroxydicarbonate,di(2-ethylhexyl) peroxydicarbonate, 1,1-dimethyl-3-hydroxybutylperoxyneodecanoate, α-cumyl peroxyneoheptanoate, t-amylperoxyneodecanoate, t-butyl peroxyneodecanoate, t-amyl peroxypivalate,t-butyl peroxypivalate, 2,5-dimethyl 2,5-di (2-ethylhexanoyl peroxy)hexane, t-amyl peroxy-2-ethyl-hexanoate, t-butylperoxy-2-ethylhexanoate, t-butyl peroxyacetate, di-t-amyl peroxyacetate,t-butyl peroxide, di-t-amyl peroxide,2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, cumene hydroperoxide,1,1-di-(t-butylperoxy)-3,3,5-trimethyl-cyclohexane,1,1-di-(t-butylperoxy)-cyclohexane, 1,1-di-(t-amylperoxy)-cyclohexane,ethyl-3,3-di-(t-butylperoxy)-butyrate, t-amyl perbenzoate, t-butylperbenzoate, ethyl 3,3-di-(t-amylperoxy)-butyrate, and the like. Blendsof initiators can also be employed. Initiators are availablecommercially, such as Vazo initiators, which typically indicate adecomposition temperature for the initiator. Preferably the initiator isselected to have a decomposition point of about 50° C. or higher.Usefully multiple initiators are employed, either as a blend in the oilphase, or in either of the oil or water phases. Preferably initiatorsare selected to stagger the decomposition temperatures at the varioussteps, pre-polymerization, wall formation and hardening or polymerizingof the capsule wall material. For example, a first initiator in the oilphase can decompose at 55° C., to promote prepolymer formation, a secondcan decompose at 60° C. to aid forming the wall material. Optionally athird initiator can decompose at 65° C. to facilitate polymerization ofthe capsule wall material. The amount of each initiator can be typicallyas low as 0.1 weight percent or as high as 10weight percent.

Internal phase oils, or oil phase, or oil solvent or “nonsolvent for thewater phase,” used interchangeably for purposes hereof can be selectedfrom solvents and the solvents can include by way of illustration andnot limitation, ethyldiphenylmethane, butyl biphenyl ethane,benzylxylene, alkyl biphenyls such as propylbiphenyl and butylbiphenyl,dialkyl phthalates e.g. dibutyl phthalate, dioctylphthalate, dinonylphthalate and ditridecylphthalate; 2,2,4-trimethyl-1,3-pentanedioldiisobutyrate, alkyl benzenes such as dodecyl benzene; alkyl or aralkylbenzoates such as benzyl benzoate; diaryl ethers, di(aralkyl)ethers andaryl aralkyl ethers, ethers such as diphenyl ether, dibenzyl ether andphenyl benzyl ether, liquid higher alkyl ketones (having at least 9carbon atoms), alkyl or aralky benzoates, e.g., benzyl benzoate,alkylated naphthalenes such as dipropylnaphthalene, partiallyhydrogenated terphenyls; high-boiling straight or branched chainhydrocarbons, alkaryl hydrocarbons such as toluene, vegetable oils suchas canola oil, soybean oil, corn oil, sunflower oil, or cottonseed oil,methyl esters of fatty acids derived from transesterification of canolaoil, soybean oil, cottonseed oil, corn oil, sunflower oil, pine oil,lemon oil, olive oil, or methyl ester of oleic acid, vegetable oils,esters of vegetable oils, e.g. soybean methyl ester, straight chainsaturated paraffinic aliphatic hydrocarbons of from 10 to 13 carbons.Mixtures of the above can also be employed. Common diluents such asstraight chain hydrocarbons can also be blended with the solvents, orblend of solvents. The solvent is selected on the basis ofhydrophobicity and ability to disperse or solvate the amine modifiedpolyfunctional polyvinyl monomer and the bi- or polyfunctional vinylmonomer or oligomer. “Internal phase oil” is herein to described as atype of oil material commonly able to be used as the oil in conventionalmicroencapsulation. In conventional microencapsulation, the internalphase oil ends up as the core or internal contents of the microcapsule.In the processes of the invention which involve water in oil (W/O)emulsifications, the internal phase oil is used in excess and the waterthen becomes the capsule core. The term in this context describes a typeof oil, but for clarity shall be understood as not necessarily formingthe capsule core when water in oil emulsifications are being done.Internal phase oil is describing a nonsolvent for the water phase insuch context.

The microencapsulation process in certain of the embodiments is believedto rely on the organic acid for formation of a changed species thatdrives the wall material to the oil water interface.

The size of the capsules can be controlled by adjusting the speed ofagitation. Smaller size dispersions are achieved through fasteragitation resulting in smaller capsules.

Emulsifying agents or protective colloids can be conveniently employedto facilitate dispersion. Such materials for example includecarboxylated or partially hydrolyzed polyvinyl alcohol, methylcellulose, and various latex materials, stearates, lecithins, andvarious surfactants.

The microcapsules according to the invention can be used tomicroencapsulate various core materials such as chromogens and dyes,flavorants, perfumes, sweeteners, fragrances, oils, fats, pigments,cleaning oils, pharmaceuticals, pharmaceutical oils, perfume oils, moldinhibitors, antimicrobial agents, adhesives, phase change materials,scents, fertilizers, nutrients, and herbicides by way of illustrationand without limitation.

Microencapsulation can facilitate processing by increasing particle sizeor by converting liquids into free flowing solids. The largest volumeapplications of microcapsules are in imaging systems such as carbonlesspapers.

The microcapsule wall can serve the purpose of extending shelf life,stabilize and protect the core material, mask strong flavors, or protectcontents so that they are available to participate in reactions such asimaging or adhesive formation when the capsule wall is ruptured,sheared, fractured, broken or melted.

The core material can be a minor or major constituent of the materialencapsulated by the microcapsules. If the core material can function asthe oil or water solvent in the capsules, it is possible to make thecore material the major or total material encapsulated. Usually however,the core material is from 0.01 to 99 weight percent of the capsuleinternal contents, preferably 0.01 to about 65 by weight of the capsuleinternal contents, and more preferably from 0.1 to about 45% by weightof the capsule internal contents. With certain especially potentmaterials, the core can be at just trace quantities.

In the alternative embodiment, any of the heating steps in themicroencapsulation process can be replaced with a UV or light induced orelectron beam induced free radical generation step.

More particularly, in this alternative embodiment the invention is aprocess of obtaining microcapsules by dispersing an oil soluble aminemodified polyfunctional monomer or oligomer and an oil soluble bi- orpolyfunctional vinyl monomer or oligomer along with a UV initiator.Optionally a visible light induced free radical generator could also beused. An organic acid is also added to the internal phase oil. Thisdispersion is then subjected to UV light to form a prepolymer. To thisinternal phase oil and prepolymer, a water phase is added comprising adispersion in water of an anionic emulsifier. Optionally either a UVinitiator or alternatively thermal initiator or alternatively noinitiator is added to the water phase. The water phase is emulsifiedinto the oil phase (W/O), or alternatively an excess of the water phaseis used and the oil phase is emulsified into the water phase (O/W).Depending on the type of initiator or initiators, the dispersion is thensubjected to UV light or heated (as appropriate to the initiator) togenerate free radicals.

As polymerization progresses, microcapsule wall material forms at theinterface of the water and oil phases. A third UV exposure or heatingstep is used to further polymerize or harden the formed wall material.

Similar substitution of UV initiator can be made in any of themicroencapsulation processes described herein and by substitution of arespective UV exposure step for the respective thermal heating step.

UV initiators include benzophenone; acetophenone; benzil; benzaldehyde;o-chlorobenzaldehyde; xanthone; thioxanthone; 9,10-anthraquinone;1-hydroxycyclohexyl phenyl ketone; 2,2-diethoxyacetophenone;dimethoxyphenylacetophenone; methyl diethanolamine;dimethylaminobenzoate; 2-hydroxy-2-methyl-1-phenylpropane-1-one;2,2-di-sec-butoxyacetophenone; 2,2-dimethoxy-1,2-diphenylethan-1-one;dimethoxyketal; and phenyl glyoxal.2,2′-diethoxyacetophenone,hydroxycyclohexyl phenyl ketone, alpha-hydroxyketones,alpha-amino-ketones, alpha and beta naphthyl carbonyl compounds, benzoinethers such as benzoin methyl ether, benzil, benzil ketals such asbenzil dimethyl ketal, acetophenone, fluorenone,2-hydroxy-2-methyl-1-phenylpropan-1-one. UV initiators of this kind areavailable commercially, e.g., IRGACURE 184™ or DEGACURE 1173™ from Ciba.Thermal initiators are available from DuPont. The fraction of thephotoinitiator in any of the water or oil phase is approximately fromabout 0.1 to 10%, preferably 0.1 to about 6% by weight, more preferably0.5 to 2.5 weight percent. Similar weight percent ranges can also beapplied to the thermal initiators.

UV initiators can be included in substitution as an alternate initiatorsystem (for any heating step or steps of the encapsulation process, oras an additional initiator system. This produces an initiator system forpolymerization or oligomerization using a dual cure method or optionalthermal or optional light or optional UV initiated method by appropriateselection of initiator and initiation method or methods. In analternative embodiment of the invention, azo compounds that can beexcited or split by UV light or high-energy radiation are used alone orin combination with thermal free radical initiators. In a yetalternative embodiment, the combination of thermal and UV initiators isformed only by azo compounds.

In a yet further embodiment, for specialized microencapsulationprocesses, the use of initiators, e.g., thioxanthones, phosphine oxides,metallocenes, tertiary aminobenzenes or tertiary aminobenzophenones,which break down into free radicals on exposure to visible light iseffectively used. Such microencapsulation systems however typicallyrequire special handling of the system to prevent prematurepolymerization or oligomerization by appropriate control of lightingconditions.

For light activated microencapsulation, the use of UV initiators arepreferred, or a combination of UV initiators and thermal free radicalinitiators. This combination can impart considerable versatility to themicroencapsulation steps of the process where any step or steps of themicroencapsulation process then can be initiated either by appropriateselection of an initiator decomposing at specific temperatures ordecomposing under specific light conditions.

In a yet further embodiment, with appropriate selection of monomers andinitiators, the respective monomers in the process can be polymerized oroligomerized using some suitable means such as heat (used with thermalinitiators) or UV light (for use with UV initiators), or electron beam.When replacing the UV radiation with electron beam, the addition ofinitiators is not absolutely essential or amounts employed can bereduced. Options for individual heating steps of the encapsulationprocess include the freedom to use in substitution for any heating step,the use of visible light with suitable initiators, the use of UV lightwith suitable UV initiators, or ionizing radiation (e.g. electron beamor gamma ray) without initiators or reduced amounts of initiator.

UV initiators may be selected from those organic chemical compoundsconventionally employed to promote UV-initiated formation of radicals. Apreferred UV initiator is 1-hydroxycyclohexyl phenyl ketone because ofthe rapidity with which it generates free radicals when exposed to UVradiation. Mixtures of UV initiators or mixtures with thermal initiatorsmay also be used. This is often desirable because it provides moreefficient production of radicals in certain cases. In general, the UVinitiator will be present in an amount of 0.1 to 10.0 weight percent inany of the water or oil phases, based on the total weight of allconstituents. However, it is preferable to use between 0.5-2.5 weightpercent UV initiator, most preferably 0.5-1.0 weight percent UVinitiator, based on total weight.

The amount of each initiator, thermal, UV or light, that is employed canvary, and is dependent upon factors such as the monomer or oligomermaterial that is polymerized or further oligomerized. Typically, theamount of initiator ranges from about 0.1 to about 6 percent, and oftenabout 1 to about 3 percent, based on the weight of all constituents.

EXAMPLES Example 1 Oil in Water Capsules

Water Phase: 25 grams acrylic acid butyl acrylate copolymer 2 grams4,4′-azobis(4-cyano valeric acid) 300 grams Water 10 grams 5% NaOHInternal Phase: 7.5 grams Amine modified polyether acrylate oligomer17.5 grams Diethylene glycol dimethacrylate 1.8 grams Monobutyl maleate247.5 grams Butyl diphenyl methane and butyl diphenyl ethane blend 1gram 2,2′-azobis(2,4-dimethylvaleronitrile) 2 grams(2,2′-azobismethylbutyronitrile) 2.5 grams Indolyl red

The internal phase is mixed with stirring for one hour under a nitrogenblanket and brought to a temperature of 65° C. and maintained at thistemperature. The water phase components are also mixed with stirring.The oil phase components are blended at high speed. The water phase isadded to the internal phase and milled for an additional two hours at65° C. to achieve a median particle size of about 3.6 μm. Thetemperature was maintained along with continuous stirring for fourhours; and then heating was increased to 90° C. for eight hours.

The resultant oil in water capsules had a size of about 4.3 μm.

Similar capsules are also preparable using diethylene glycol diacrylate.

Example 2

Water Phase: 300 grams Water 25 grams acrylic acid butyl acrylatecopolymer 2 grams 4,4′-azobis(4-cyano valeric acid) 10 grams 5% NaOHInternal Phase: 247.5 grams Butyl diphenylmethane and butyldiphenylethane blend 2.5 grams Indolyl red dye 7.5 grams Amine modifiedpolyether acrylate oligomer (CN 551 ™, Sartomer, Exton, Pennsylvania)17.5 grams Ethylene glycol dimethacrylate 1.5 grams2,2′-azobis(2,4-dimethylvaleronitrile) 0.5 grams(2,2′-azobismethylbutyronitrile) 1.0 grams 1,1′-azobis(cyanocyclohexane1.8 grams Monobutylmaleate

The internal phase is mixed with stirring for one hour at 70° C. under anitrogen blanket. The water phase components are also blended withstirring. The oil phase components are blended at high speed. The waterphase is added to the internal phase and milled for an additional twohours at 70° C. to achieve a median particle size of 3.7 μm. Thetemperature was maintained along with continuous stirring for four hoursand then heating was increased to 90° C. for eight hours. The resultantoil in water capsules had a size of about 4.2 μm.

Example 3

Permeability of resultant capsules Wall Material (methanol extraction)Diethylene glycol dimethacrylate 3.77 Diethylene glycol diacrylate 15.89Aromatic urethane acrylate 0.00 Urethane acrylate 17.80 Tetraethyleneglycol diacrylate 41.36 1,4-butane diol diacrylate 1.61 Ethylene glycoldimethacrylate 0

Permeability can be controlled through wall material selection, throughcontrol of the degree of cross-linking, by controlling temperature ofcross-linking, by controlling length of time of cross-linking, or withUV initiated systems by controlling intensity of UV light and duration.

Permeability is determined by extracting for 5 seconds using methanoland measuring relative coloration of extracted dye.

Example 4

Water Phase: 300 grams Water 25 grams Butyl diphenyl methane and butyldiphenyl ethane blend 10 grams 5% NaOH 2 grams 4,4′-azobis(4-cyanovaleric acid) Internal Phase: 247.5 grams Dioctyl phthalate 2.5 gramsIndolyl red 7.5 grams Amine modified polyester acrylate oligomer 17.5grams Tetraethylene glycol diacrylate 1.8 grams Monobutyl maleate 1 gram2,2′-azobis(2,4- dimethylvaleronitrile) 2 grams (2,2′-azobismethylbutyronitrile) 2.5 grams Indolyl red

Following the procedure described in Example 1, capsules were obtained7.8 μm median diameter.

Example 5 Water in Oil Capsules

Oil Phase: 247.5 grams Butyl diphenylmethane and butyl diphenyl ethaneblend 3.3 grams Amine modified polyether acrylate oligomer (CN 551 ™,Sartomer, Exton, Pennsylvania) 7.7 grams Ethylene glycol dimethacrylate0.9 grams 2,2′-azobis(2,4-dimethylvaleronitrile) 0.3 grams(2,2′-azobismethylbutyronitrile) 0.8 grams Monobutyl maleate WaterPhase: 66 grams Water 5.5 grams Acrylic acid butyl acrylate copolymer2.8 grams 5% NaOH 0.4 grams 4,4′-azobis(4-cyano valeric acid) 3 dropsBlue dye

The oil phase was mixed and heated to 70° C. for one hour. The waterphase components are also mixed with stirring. The water phase is addedto the oil phase and milled for 2 hours at 65° C. under a nitrogenblanket. Gradually increase the temperature to 70° C. and maintain withstirring for about 9 hours. Unaggregated capsules were observed.

Example 6

Oil Phase: 330 grams Toluene 3.3 grams Amine modified polyether acrylateoligomer 7.7 grams Ethylene glycol dimethacrylate 1.2 grams2,2′-azobis(2,4-dimethylvaleronitrile) 0.8 grams Monobutyl maleate WaterPhase: 66 grams Water 5.5 grams Acrylic butylacrylate copolymer 2.8grams 5% NaOH 1 drop Blue dye (Brilliant Bond Blue)

Using the procedure of Example 5 except initial heating was carried outat 65° C., water in oil capsules were observed.

Example 7

Oil Phase 400 grams Toluene (External 3.3 grams Amine modified polyetheracrylate Phase): oligomer (CN 551 ™, Sartomer, Exton, Pennsylvania) 7.7grams Trimethylolpropane triacrylate 0.9 grams(2,2′-azobismethylbutyronitrile) 0.8 grams Monobutyl maleate InternalPhase: 66 grams Water 5.5 grams Acrylic butylacrylate copolymer 2.8grams 5% NaOH 0.8 grams 4,4′-azobis(4-cyano valeric acid) 1 drop Bluedye

Using the procedure of Example 5 except initial heating was carried outat 60° C., water in oil capsules were observed.

Example 8

Water Phase 2.5 grams polyacrylic acid 75 grams Water Oil Phase: 12.5grams Amine modified polyether acrylate 12.5 grams Diethylene glycoldimethacrylate 0.25 Monobutyl maleate 1.0 grams2,2′-azobis(2,4-dimethylvaleronitrile) 2.5 grams Indolyl red dye (I6B)221.75 grams Soybean oil methyl ester

The oil phase components were placed in a 25° C. steel reactor, withmixing at 250 rpm under a nitrogen blanket at 200 cc/mm. The oil phasewas heated to 70° C. for 90 minutes. The water phase was added and theblend milled at 2500 rpm. 15 grams of NaOH were added dropwise. Stirringwas continued and solution maintained at 70° C. for 90 minutes. Heatingwas then increased to 90° for twelve hours.

Measured permeability of formed microcapsules was 52%.

Example 9

Oil Phase 7.5 grams Amine modified polyether acrylate 17.5 gramsEthylene glycol dimethacrylate 1.8 grams Monobutyl maleate 223.7 gramsFragrance oil (lemon oil) 1 gram 2,2′-azobis(2,4-dimethylvaleronitrile)1 gram (2,2′-azobismethylbutyronitrile) 1 gram1,1′-azobis(cyanocyclohexane Water Phase 300 grams Distilled water 25grams Polyacrylic acid 10 grams 5% NaOH 2 grams 4,4′-azobis(4-cyanovaleric acid)

Mix the oil phase and stir for 1hour under a nitrogen blanket. Stir at300 rpm. Add water phase and stir with magnetic stirrer. Heat to 70° C.for about one hour. Mill at 70° C. for 3 hours increasing speed to 400rpm. End of milling size is 12.4 rpm. Heat with agitation to 90° C. andhold for 8 hours. Oil in water capsules encapsulate lemon oil.

Example 10

Oil Phase 12.5 grams CN 550 ™ amine modified polyether acrylate oligomer(Sartomer, Exton, Pennsylvania) 12.5 grams Diethylene glycoldimethacrylate 0.25 grams Monobutyl maleate 2.5 grams Red dye I6B 1 gram2,2′-azobis(2,4-dimethylvaleronitrile) 221.75 grams Soybean oil methylester Water Phase 25 grams polyacrylic acid 475 grams Water

Other amine modified polyether acrylate oligomers can typically befreely substituted in the examples. Blend oil phase with stirring at 250rpm under a nitrogen blanket at 200 cc/mm. Heat from 25° C. to 70° C.for one hour. Hold for an additional thirty minutes. Add water phase andmill at 2500 rpm. Add 15 grams of 5% NaOH. Stir at 500 rpm and hold at70° C. for 90 minutes. Increase temperature to 90° C. for 12 hours.

Measured permeability of the capsules was 52%.

Example 11

Oil Phase 10 grams CN 501 ™ amine modified polyether acrylate oligomer(Sartomer, Exton, Pennsylvania) 15 grams Diethylene glycol diacrylate0.25 grams Monobutyl maleate 2.5 grams Red dye I6B 0.5 grams2,2′-azobis(2,4-dimethylvaleronitrile) 221.75 grams Soybean oil andmethyl ester Water Phase 25 grams polyacrylic acid 475 grams Water

Oil phase is added to the reactor and mixed at 250 rpm under a nitrogenblanket at 200 cc/mm. The solution is heated from 25° C. to 65° C. forsixty minutes. The temperature is held at 65° C. for 60 minutes. Thewater phase is added and mixed at 2500 rpm. Temperature is held at 65°C. for 16 hours with high speed stirring.

Example 12

Oil Phase 12.5 grams amine modified polyether acrylate oligomer 25 gramsAliphatic urethane acrylate Tg 90° C. 2.7 grams Monobutyl maleate 2.5grams Red dye, I6B 1 gram 2,2′-azobis(2,4-dimethylvaleronitrile) 2 grams(2,2′-azobismethylbutyronitrile) 247.5 grams sec-butyl diphenyl methaneand sec-buty diphenyl ethane Water Phase 25 grams Polyacrylate 300 gramsWater 9 grams 5% NaOH 2 grams 4,4′-azobis(4-cyano valeric acid)

Blend and heat the materials according to the process of Example 11.

Example 13

Oil Phase 12.5 grams amine modified polyether acrylate oligomer 12.5grams Trimethylol propane triacrylate 2.7 grams Monobutyl maleate 2.6grams I6B, red dye 1 gram 2,2′-azobis(2,4-dimethylvaleronitrile) 2 grams(2,2′-azobismethylbutyronitrile) 247.5 grams sec-butyl diphenyl methaneand sec-buty diphenyl ethane Water Phase 25 grams Acrylic acid butylacrylate copolymer 300 grams Water 9 grams 5% NaOH 2 grams4,4′-azobis(4-cyano valeric acid)

The oil phase is placed in a reactor at 25° C. and stirred at 300 rpmunder a nitrogen blanket at 200 cc/min. The oil phase is heated from 25°C. to 65° C. for an hour and held at 65° C. for a n hour and held at 65°C. for an additional hour. The water phase is added and then millingstarted at 3000 rpm and continued for two hours. End of mill size 50% at7.1 microns. 200 grams of water is added and mixing contained at 3000rpm. Temperature is held at 65° C. for five hours and then thetemperature is increased to 90° C. for about 9 hours.

Example 14

Oil Phase 7.5 grams CN 551 ™ Amine modified polyether acrylate oligomer(Sartomer, Exton, Pennsylvania) 17.5 grams Pentaerythritol triacryate1.8 grams Monobutyl maleate 2.5 grams I6B, red dye 247.5 grams sec-butyldiphenyl methane and sec-butyl diphenyl ethane 1 gram2,2′-azobis(2,4-dimethylvaleronitrile) 1 gram(2,2′-azobismethylbutyronitrile) Water Phase 25 grams Acrylic acid butylacrylate copolymer 2 grams 4,4′-azobis(4-cyano valeric acid) 300 gramsWater 10 grams 5% NaOH

Blend and heat the materials according to the process of Example 13.

Example 15

Oil Phase 7.5 grams Amine modified polyether acrylate 17.5 gramsEthylene glycol dimethacrylate 1.8 grams Monobutyl maleate 223.7 gramsPine oil (or optionally pine oil dissolved in toluene) 3 grams1-hydroxycyclohexyl phenyl ketone Water Phase 300 grams Distilled water25 grams Polyacrylic acid 10 grams 5% NaOH

Mix the oil phase and stir for 1 hour under a nitrogen blanket. Stir at300 rpm. Add water phase and stir with magnetic stirrer. At the sametime, expose to UV light for about three hours. Mill at 70° C. for 3hours increasing speed to 400 rpm while continuing UV exposure. Use endof milling size of 12.4.

Example 16

Oil Phase 7.5 grams CN 551 ™ amine modified polyether acrylate oligomer(Sartomer, Exton, Pennsylvania) 17.5 grams CN 999 ™ aromaticdifunctional urethane acrylate (Sartomer, Exton, Pennsylvania) 1.8 gramsMonobutyl maleate 2.5 grams I6B, red dye 247.5 grams sec-butyl diphenylmethane and sec-butyl diphenyl ethane 1 gram2,2′-azobis(2,4-dimethylvaleronitrile) 2 grams benzoyl peroxide WaterPhase 2.5 grams Acrylic acid butyl acid copolymer 2 grams4,4′-azobis(4-cyano valeric acid) 300 grams Water 10 grams 5% NaOH

Blend and heat the materials using the process of Example 13 End ofmilling size is about 50% at 3.26 microns. Optionally, flavorants,sweeteners, cleaning oils, scents, pharmaceutical oils, antimicrobials,phase change materials, polishing oils, fertilizers, herbicides,perfumed oils, fragrant oils, oil soluble adhesive materials can besubstituted in any of the examples for amount of the dye or for thesolvent to prepare adhesive-containing or fragrance-containing orflavorant-containing, as the case may be, microcapsules. The oils shouldbe preferably dispersible or soluble in the internal phase.

Unless otherwise indicated herein, all measurements are on the basis ofweight and in the metric system. The principles, preferred embodimentsand modes of operation of the present invention have been described inthe foregoing specification. The invention which is intended to beprotected herein, however, is not to be construed as limited to theparticular forms disclosed, since three are to be regarded asillustrative rather than restrictive variations and changes can be madeby those skilled in the art without departing from the spirit and scopeof the invention.

1. A process for preparing microcapsules encapsulating a water phase,the process comprising: dispersing an oil soluble amine modifiedpolyfunctional polyvinyl monomer or oligomer and an oil soluble bi- orpolyfunctional vinyl monomer or oligomer along with a free radicalinitiator and an organic acid into an excess of an oil phase which is anonsolvent for the water phase; the organic acid selected from the groupconsisting of monoalkyl maleate, alkyl benzene sulfonic acid, andalkyldiphenyloxide sulfonic acid; a first heating step comprising,heating for a time and temperature sufficient to oligomerize or furtheroligomerize the amine modified polyfunctional polyvinyl monomer oroligomer and oil soluble bi- or polyfunctional vinyl monomer oligomerforming a pre-polymer; adding to the oil phase a water phase comprisinga dispersion in water of an anionic emulsifier and a free radicalinitiator and a core material, and emulsifying the water phase into theoil phase forming droplets of the water phase dispersed in the oilphase; a second heating step comprising, heating for a time andtemperature sufficient to decompose the free radical initiators in theoil and water phases; thereby forming microcapsule wall material at theinterface of the water and oil phases, the microcapsules encapsulatingthe water phase droplets; and a third heating step comprising heating toa temperature equal to or greater than the second heating steptemperature for a time sufficient to polymerize the wall material. 2.The process for preparing microcapsules according to claim 1 wherein afree radical initiator is selected from an azo or peroxy initiator. 3.The process according to claim 1 wherein the oligomerization isaccomplished by heating, in the first heating step, to at least 55° C.for at least one hour to form the prepolymer.
 4. The process accordingto claim 1 wherein the amine modified polyvinyl monomer is selected fromamine modified ethoxylated trimethylol propane triacrylate, diacrylateamine, dimethacrylate amine, amine modified polyetheracrylate, and aminemodified polyethermethacrylate.
 5. The process according to claim 1wherein the bi- or polyfunctional vinyl monomer or oligomer is selectedfrom a polyacrylate, a polymethacrylate, a dimethacrylate, a diacrylate,a triacrylate, diethylene glycol dimethacrylate,pentaerythritoltriacrylate, trimethylol propane triacrylate, urethanediacrylate, urethane dimethacrylate, ethoxylated aliphatic difunctionalurethane acrylate, and ethoxylated aliphatic difunctional urethanemethacrylate.
 6. The process according to claim 1 wherein the emulsifieris selected from polyacrylic acid, polymethacrylic acid, acrylic acidalkyl acrylate copolymer, alkyl succinamate, an alkylaryl sulfonic acidsalt or an alkyl sulfate salt.
 7. The process according to claim 1wherein the organic acid is selected from carboxy acid, organic sulfonicacid, or monoalkyl maleate.
 8. The process according to claim 1 whereinthe third heating step comprises heating to at least 90° C. for at leastthree hours.
 9. The process according to claim 1 wherein the initiatorin the oil phase decomposes at a first temperature and the initiator inthe water phase decomposes at a second temperature.